#include <iostream>
#include <type_traits>

template <typename T>
void checkType()
{
    // if (std::is_integral_v<T>) {
    if (std::is_integral<T>::value) {
        std::cout << "`T` is an integral type.\n";
    } else {
        std::cout << "`T` is not an integral type.\n";
    }
}

int main()
{
    checkType<int>(); // 输出：`T` is an integral type.
    checkType<double>(); // 输出：`T` is not an integral type.
    return 0;
}